1. Field of the Invention
This invention relates to a method for solubilizing poly(1-3)glucopyranose in a medium compatible with a subsequent incorporation into a cosmetic preparation.
2. Description of the Prior Art
Its object is also a cosmetic composition using poly(1-3)glucopyranose solubilized by said method.
It should be recalled that poly(1-3)glucopyranose is a long-chain polysaccharide extracted e.g. from yeast cell walls, and comes in the form of a beige-colored, odourless powder that is insoluble in water, and is marketed by Immudyne Inc. under the "Nayad" trademark. It is classified in the chemical category of homogeneous polyhexoses, a category which includes, inter alia:
the dextrans which are soluble in an aqueous medium, forming colloidal solutions of viscosity varying as a function of molecular weight, PA1 amylum which is not soluble in water but which, when brought to 100.degree. C., forms well-known starch, PA1 cellulose which is insoluble in water and in the usual solvents. PA1 The neutral polysaccharides such as dextran, levan, scleroglucane can be directly solubilized by DMSO ((CH.sub.3).sub.2 SO). However, this solvent has the drawback of being incompatible with incorporation into a cosmetic product. PA1 The combined action of 4-methylmorpholine-n-oxide and DMSO enables an overall solubilizing of polysaccharides other than starch. However, in this case, a 120.degree. C. heating stage is required to extract the products. Because of this, the integrity of the poly(1-3)glucopyranose cannot be guaranteed and, furthermore, this method is subject to the same incompatibility problems as above. PA1 The utilisation of sodium hydroxide, NaOH, which, however, produces variations in the viscosity of the scleroglucane, has not enabled significant results to be obtained in the case of poly(1-3)glucopyranose. These observations tend to confirm that poly(1-3) glucopyranose is not really a scleroglucane.
Studies conducted to date on the solubilization of polysaccharides other than starches reveal that:
These studies have not enabled the determination of a solubilizing method applicable to poly(1-3)glucopyranose and compatible with cosmetic applications.
The filing party has therefore conducted tests using agents such as polyalcohols to wet the powder and facilitate dispersion thereof in water.
Accordingly, a series of experiments have been conducted with a view to assessing the solubility of glucopyranose in a range of sorbitol/distilled water mixtures, at temperatures ranging from +25.degree. C. to +100.degree. C., in order to select the solvent enabling optimal dissolution of the product at the lowest possible temperature.
In the course of these experiments, the solutions were subjected to rising temperatures (by increments of 10.degree. C. up to 100.degree. C.) for periods of one to two hours, with a rest time of approximately half an hour between each temperature stage. Once the appearance of the solutions so permitted (homogeneity and absence of aggregates in suspension), a spectrophotometric reading was taken at 600 nm in order to assess the degree of opacity.
All solutions were maintained at room temperature for 48 hours. Upon expiry of this period, appearance and absorbance at 600 nm were recorded.
The results obtained have been set forth in Table I hereafter which only takes into account temperatures from 50.degree. C. up (absorbance could not be measured below this temperature as the majority of solutions were not homogeneous).
They show that irrespective of the composition of the solvent mixture, a heating stage is indispensable for dispersion of the active principle, the minimum temperature being 50.degree. C. Moreover, as the proportion of sorbitol increases, dispersion becomes easier at low temperature and the opacity of the mixture decreases. Furthermore, the threshold of temperature required to obtain an apparent dissolution of the active principle decreases as the proportion of sorbitol is increased.
TABLE I ______________________________________ Composition of the solvent mixture TEMPERATURE Water Sorbitol +50.degree. C. +60.degree. C. +80.degree. C. +100.degree. C. (V) (V) 1 h 2 h 1 h 2 h 1 h 1 h ______________________________________ 100 0 1.368 1.419 1.387 1.361 1.299 1.369 90 10 1.347 1.351 1.335 1.310 1.293 1.292 80 20 1.259 1,255 1,240 1.246 1.234 1.206 70 30 1.150 1.142 1.110 1.096 1.080 1.098 60 40 1.035 1.029 1.002 0.997 0.975 0.996 50 50 0.912 0.888 0.849 0.822 0.817 0.838 40 60 0.774 0.774 0.736 0.730 0.704 0.720 30 70 0.784 0.716 0.668 0.653 0.609 0.633 20 80 0.637 0.594 0.562 0.551 0.512 0.535 10 90 0.504 0.492 0.482 0.467 0.438 0.449 0 100 0.477 0.433 0.418 0.420 0.377 0.394 ______________________________________
From 80% sorbitol upwards, up to 48 hours at rest, the solution remains stable at room temperature and then forms a deposit which can disappear when the solution is stirred. It is unstable from 0.degree. C. to 50.degree. C.
It is obvious that even if these results are encouraging and constitute real progress, in particular for percentages of sorbitol of the order of 90%, the instabilities observed after 48 hours and at 0.degree. C. and 50.degree. C. continue to be a considerable inconvenience.